Ambipolar Landau levels and strong band-selective carrier interactions in monolayer WSe$_2$

TL;DR

This study uses LL spectroscopy to reveal the complex electronic structure and strong many-body interactions in monolayer WSe$_2$, highlighting its potential for hosting novel correlated-electron phenomena.

Contribution

First comprehensive mapping of ambipolar Landau levels in monolayer WSe$_2$, demonstrating strong Zeeman effects and many-body interactions in both electron and hole bands.

Findings

Landau levels differ between electron and hole bands

Zeeman splitting in the valence band is significantly larger than cyclotron energy

Zeeman effects strongly depend on doping levels

Abstract

Monolayers (MLs) of transition metal dichalcogenides (TMDs) exhibit unusual electrical behavior under magnetic fields due to their intrinsic spin-orbit coupling and lack of inversion symmetry. While recent experiments have also identified the critical role of carrier interactions within these materials, a complete mapping of the ambipolar Landau level (LL) sequence has remained elusive. Here, we use single-electron transistors to perform LL spectroscopy in ML WSe$_2$, for the first time providing a comprehensive picture of the electronic structure of a ML TMD for both electrons and holes. We find that the LLs differ notably between the two bands, and follow a unique sequence in the valence band (VB) that is dominated by strong Zeeman effects. The Zeeman splitting in the VB is several times higher than the cyclotron energy, far exceeding the predictions of a single-particle model, and moreover tunes significantly with doping. This implies exceptionally strong many-body interactions, and suggests that ML WSe$_2$ can serve as a host for new correlated-electron phenomena.